A truncated version of the nef gene of simian immunodeficiency virus SIVmac239 capable of encoding amino acids 98 to 263 was used as bait to screen a cDNA library from activated lymphocytes in a yeast two-hyrid system The zeta chain of the T-cell receptor (TCR ) was found to interact specifically not only with truncated SIV nef in yeast cells but also with full-length glutathione S-transferase (GST)-SIVnef fusion protein in vitro Coimmunoprecipitation of TCR with full-length SIV nef was demonstrated in transfected Jurkat cells and in Cos 18 cells which express the cytoplasmic domain of TCR fused to the external domain of CD8 via the CD8 transmembrane domain Using a series of nef deletion mutants, we have mapped the binding site within the central core domain of nef (amino acids 98 to 235) Binding of TCR was specific for nef isolated from SIVmac239, SIVsmH4, and human immunodeficiency virus (HIV)-2ST and was not detected with nef from five different HIV-1 i sola tes An active tyrosine kinase was coprecipitated with nef-TCR complexes from Jurkat cells but not from J CAM1 6 cells which lack a functional Lck tyrosine kinase These results demonstrate a specific association of SIV and HIV-2 nef, but not HIV-1 nef, with TCR PUBLICATIONS Howe, A Y M, Jung, JU and Desrosiers, RC Zeta chain of the t-cell receptor interacts with nef of simian immunodeficiency virus and human immunodeficiency virus type 2 J Virol 1998; 72:9827-9834